This invention relates to electromagnetic wave communication systems, and in particular to means for eliminating the effects of multiple interference sources on such systems.
Commonly, adaptive control loops or adaptive sidelobe cancellers are used to generate cancellation signals in response to interference signals. However, adaptive sidelobe cancellers have in many cases yielded poor performance when field tested against multiple jammers. One of the key factors contributing to this degradation is that loop gain for weak jammers in the presence of a dominant jammer falls rapidly (square law) as a function of weak jammer power level. A significant result of this effect is that little or no cancellation may be obtained for the weaker jammers while the dominant jammer is suppressed to system noise and in fact well below the weaker jammers. There currently exists, therefore, the need for a sidelobe cancelling means that simultaneously discriminates against multiple jamming signals and that further effectively discriminates against multiple weak jammers in the presence of a dominant jammer. The present invention is directed toward satisfying that need.